Method of reclaiming sand



May 15, 1951 WHQRTH 2,553,318

, METHOD OF RECLAIMING SAND Filed Ma 20, 1949 Patented May 15, 1951Walter Horth, Wilmette, 111., assignor, by mesne, assignments, toHerbert S. Simpson,.Evanston,

111., .as trustee Application May 20, 1949, Serial No. 94,472

1 Claim.

This invention relates to improvements in a method of reclaiming sand.More particularly, this invention has to do with a novel method ofheating sand in a furnace to remove carbonaceous material therefromwhich has been deposited on the sand during a molding operation in afoundry.

In foundry work, sand is used in making molds. During the preparation ofthis sand, oil, cereal binders, wood .flour, pitch, sea-coal and otherhydro-carbons are added to the sand to give it certain desirable moldingcharacteristics; After the castingoperation is completed, some of thismaterial willremain'in the sand as carbonaceous deposits which must beremoved during the reconditioning. process.

Various types .of apparatus have been used with some success forremoving these deposits from the sand particles. The usual process is toapply heat to the sand to burn off these carbonaceous deposits. It is animportant object of this invention to provide a novel, more efficientmethod of burningsuch deposits from the sand.

Another object of this invention is to provide a novelmethod of bringingheated air into intimate contact with the sand grains.

A further object of this invention is to provide a method of usingcompressed air to transfer heated gases throughout the sand that isbeing processed.

A still further object of this invention is to provide a method ofreclaiming sand requiring a minimum amount of equipment. and vfloorspace tocarry out the operation.

A feature of this invention is the provision of a generally cylindricalvertical furnace havingan upper charging door and a lower dischargeopening. Three batches of sand, a lower, a middle and an upper batch,are deposited in superimposed relation in the furnace. The middle batchis disposed in a central combustion zone of the furnace, where heat isapplied thereto by means of a burner until the temperature of the sandis brought up to about 1700 F. Heat from this combustion actionpre-heats the upper batch of sand which is immediately. above the middlebatch. When the temperature of the middle batch is at about 1700 F. theburner is turned off and the lower batch of sand is discharged out thebottom discharge passage and the middle batch is moved downwardly fromthe combustion zone to the bottom cooling zone of the furnace while anew batch of sand is added at the top of the furnace and is deposited inthe preheating zone. Compressed air is introduced to the previouslyprocessed sand which is now in the cooling zone of the furnace in apulsating fashion created by operating an air supply valve and adischarge valve in a predetermined cycle so that the pressure in thefurnace will pulsate in a wide range ultimately permeating the voidspaces between the sand grains and inathe sand lumps and releasing thecombustion gases caused by the oxidation of the carbon on the sandgrains.

By passing through the lower batch of sand, the compressed air is heatedto a temperature which supports the combustion of the carbon on the sandgrains. When this air reaches the middle batch in the combustion zonethe carbon deposits on the sand and thiszone will be burned elf. Theheat from this combustion pre-heats the new batch of sand in the upperpre-heating zone. When combustion is completed in the middle orcombustion zone, the lower batch which has been cooled by the passage ofair therethrough is discharged from the bottom of the furnace permittingthe batch in the combustion chamber to be dropped to the lower position.Air under pressure is then directed through the new lower batch andcombustion ensues once more in the middle or combustionzone effectingthe pre-heating of the new batch in the preheating zone.

Thus each batch is charged :at ambient temperatures and pro-heated inthe upper zone, carbon particles are burned off the sand in the batch inthe combustion zone and the sand is cooled when the batch reaches thelower zone.

Other and further important features, objects and advantages of thepresent invention will be apparent to those skilled in the art from thefollowing detailed description of the annexed sheets of drawings.

On the drawings:

Figure 1 is a more or less diagrammatic vertical sectional view takenthrough the center of a sand reclamation furnace constructed inaccordance with the teachings of the present invention.

As shown on the drawings:

The reference numeral 10 indicates a vertical, cylindrical shell of thefurnace. The shell, which is lined with refractory material 12, has anopen top on which is suitably secured a bonnet l4. The bonnet I 4 ispartitioned to form a sand receiving or storage chamber 16 and anannular gas discharge chamber l8 which is disposed around the storagechamber IB and is in communication with the open top of the furnace.

Delivery of sand from the storage chamber It to the furnace iscontrolled by a frusto-conical valve I 9 that is arranged to open orclose a frustoconical port 20 at the lower end of the discharge chamber.The valve l 9 may be conveniently operated by a double-acting fluidcylinder 2| having connections 22 and 24 to a source of fluid underpressure. The cylinder may be mounted on the frame of the furnace or ona separate support structure.

An exhaust pipe 26 is connected to the annular gas'discharge chamber [8.A pulsating discharge and relief valve 28 is connected in the exhaustpipe 26 to control the discharge of gases therethrough. This valve maybe of any suitable commercial type having connections for periodicallyopening and closing the valve.

At the lower end of the furnace an air manifold 30 is suitably supportedaround the shell IQ of the furnace. A plurality of discharge conduits 32pass through the wall of the furnace connecting the manifold 3i! to theinterior of the furnace. A pulsating air supply and pressure reducingvalve 34 is disposed in an air supply conduit 36 which is arranged toconnect the manifold 39 to a source of air under pressure.

At approximately one-third of the way up the side of the furnace shellthe heating manifold 40 is suitably secured therearound having dischargeopenings 42 which pass through the wall of the furnace and are arrangedto deliver heated air to the inside of the furnace. A burner 44,connected by means of aconduit 45 to a source of fuel, is arranged toheat the manifold 4% for supplying heat to the furnace.

A funnel-shaped discharge section 59 is connected to the lower end ofthe furnace having a lower opening 52 which is closed by a slidingdischarge dor'54. An opening 56 in the discharge door 54 is arranged tobe aligned with the opening 52 in the discharge funnel to permit thedischarge of sand from the furnace through the discharge door. Thisdischarge door may be conveniently operated by means of a double-actinghydraulic or pneumatic cylinder 58.

A by-pass line 60 containing a shut-off valve 62 is disposed between theburner 44 and the air supply line 36 for furnishing controlled amountsof air to the burner.

It will, of course, be understood that a suitable control mechanism suchas interconnected timed electrical relays are to be furnished with thisequipment for co-ordinating the operation of the valve l9 and thedischarge door 54 and the pulsating valves 28 and 34.

To put the novel method of reclaiming sand in operation, three batchesof sand are disposed in superimposed relation in the furnace. Thesebatches will be indicated generally by the letters A, B and C. It willbe noted that the batch A is the lowermost batch and is disposedopposite the nozzle 32 of the compressed air manifold 36. The lower endof batch B is disposed opposite the discharge nozzle 42 of the heatingmanifold 40. The burner 44 is turned on and the batch Bin the middle orcombustion zone of the furnace is heated up to approximately 1700 F. bymeans of the heated air and combustion gases passing from the manifold45 into the furnace, and upwardly through the sand charges B and C.These heated gases passing up through the batch B will cause combustionof the carbonaceous materials'deposited on the grains of sand in thisbatch and the heated combustion will cause the pre-heating of the batchCrthereabove. When the batch C has reached the temperature ofapproximately 1700 F., the burner 44 is turned off and the dischargedoor 54 is moved to the discharge position permitting the batch A to bedischarged from the furnace and the batch B and C to drop down oneposition. Thus, batch B, which has been preheated by the heatingmanifold 40 and in which the carbonation materials have beensubstantially burned from the grains of sand will now assume thelowermost position in the furnace. The charge 0 will move into themiddle or combustion zone and a new charge D (not shown) will bedeposited in the upper pre-heating zone.

Compressed air is then introduced through the air manifold 30 in apulsating fashion created. by operating the discharge valves 28 and 34in predetermined cycles, so that the pressure in the combustion chamberwill pulsate through a wide range, ultimately permeating the void spacebetween the grain sand and in the sand lumps. Thus, the combustion gasescaused by the oxidation of the carbon'on the sand grains will bereleased. By passing through the lowermost charges B, the compressed airis pro-heated to a temperature which supports combustion of the carbonon the sand grains. When the compressed air reaches the batch C in themiddle combustion zone, combustion of the carbonaceous materials on thesand grains will take place. After several minutes of operation, thecarbon on the sand grains will be combined with the oxygen in the air toform 002 and CO and will, in escaping through the charge C, havepro-heated the same. Thus, the compressed air, which was heated to acombustion temperature in the lowermost zone of the furnace as it passesthrough the previously heated batch B, moves into the combustion chamberC where the carbonaceous material is burned. The heat of combustioncauses the sand in batch D in the pre-heating chamber to be pro-heated.

After a predetermined period,-the lowermost the gases escaping from thecombustion process taking place immediately below in the combustionchamber of the furnace. When the sand reaches the combustion zone, thecarbonaceous material is burned from the grains of sand due to thecombining of the pre-heated sand with the charge of compressed air whichis pre heated by passing through the lower zone. When in the lowermostzone of the furnace, the sand is cooled by the passage of compressed airtherethrough and isfinally discharged at a cooled temperature.

The air in the air manifold 30 is charged into the furnace at ambienttemperature and heated by its passage through the lowermost batch. As itpasses through the combustion zone, it is broken down mainly intonitrogen, carbon dioxide and carbon monoxide, and in passing through thepre-heating zone the combustion gases. exchange their heat bypassingthrough the ports between the sandgrains, thus heating up thesand. Therefore, the exhaust gas temperature will also be relativelylow.

Ordinarily there will be enough combustible carbonaceous material'on thegrains in the sand in the combustion zone to supply sufiicient heat for.making up the losses in the exhaust gases, the discharge sand andthrough radiation. Thus,

this process will be substantially self-sustaining.

If it is necessary to add outside heat, additional carbon in the form ofcoke breeze may be added directly to the sand charge or in the form ofgas or oil through the pro-heat burner manifold.

While the method of this invention has been described as applying to afurnace as a batch side unit, it could also be operated continuouslywithout difficulty.

From the foregoing description it Will be recognized that there isprovided in this invention a novel method for reclaiming sand by makinguse of a furnace constructed in such a manner that it closelyapproximates a perfect heat exchanger in that it Works entirely on thecounter-flow prin ciple. Further, this novel method of reclaiming sandis operable with minimum fuel requirements since the principal cost ofthe operation will be for supplying compressed air. Similarly, theentire apparatus requires a very small floor space due to its verticalconstruction.

It Will, of course, be understood that various details or" constructionmay be varied through a Wide range and it is not the purpose of thisinvention to limit the patent granted hereon otherwise than necessitatedby the scope of the appended claim.

I claim as my invention:

A method of reclaiming foundry sand having carbon deposits thereon in anupright furnace including an air inlet and an air outlet and having anupper pre-heating zone, a middle combustion zone and a lower coolingzone, comprising depositing given batches of sand at ambient roomtemperatures in said zones of said furnace, heating the sand in saidcombustion zone to a temperature to support combustion of the carbondeposits on said sand, directing the combustion gases through thepro-heating zone to pre-heat the sand therein, discharging the sand fromsaid cooling zone and moving the sand from said combustion zone to saidcooling zone and the sand from said pre-heating zone to said combustionzone, delivering a new batch of sand to said pre-heating zone,alternately opening and closing the furnace air inlet and outlet fordirecting air under pulsating pressures through said cooling zone topro-heat the air and cool the sand therein, directing the pro-heated airthrough the pre-heated sand in the combustion chamber to cause burningof the carbon particles and directing the products of combustion throughthe sand in the pre-heating zone to pre-heat the same.

WALTER HORTH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,239,801 Voorhees .Apr. 29, 19412,412,657 Nichols Dec. 3, 1946 2,429,567 Christensen Oct. 28, 19472,436,340 Upham Feb. 17, 1948 2,458,356 Evans Jan. 4, 1949 2,477,019Utterbach July 26, 1949

